Abstract:Based on the case of a shield tunnel project operating over a deep foundation pit of an belt expressway, firstly, taking the illegal construction of the south half deep foundation pit as the breakthrough point, through the measured effects of field monitoring, detection and 3D scanning census, the adverse influence level of illegal construction on the shield tunnel is evidenced. Secondly, the safety performance and safety redundancy of the cross-section and longitudinal section of the tunnel structure are evaluated by modifying the conventional theoretical calculation and Ansys modeling analysis. And then, taking the north half construction with the optimization and protection measures as the contrast research object, through the field measured data, the division, subsection, jumping and time-limited excavation are proved. The measures of increasing the length of the bench pile, reducing the distance between the piles, increasing the thickness of the cover plate and implementing the soil filling grouting can reduce the upheaval of shield tunnel in the excavation stage and after construction. Based on this, some suggestions on the design and construction of shield tunnel across foundation pit are put forward, which can provide reference for the external operation and protection of this kind of protection zone.
